The subject invention relates to the dejittering of signals transmitted between a source and a receiving apparatus, and more particularly to the dejittering of data in a digital or digitally encoded format.
In transmitting digital data between a source and a receiving apparatus it is common for frequency distortion known as jitter and flutter to be introduced in the data and data-derived clocks. For example, jitter may be introduced when multiple tape copies are made between successive tape recorders. Particularly in satellite transmissions from satellite born recording apparatus, the problem of high frequency jitter is compounded by the transmission of the signal through space. While processors receiving data containing such jitter are relatively insensitive to low frequency flutter, the higher the frequency, the less tolerant the processors are to it, and the more errors are likely to occur. In such applications, megacycle data may exhibit jitter at kilohertz frequencies. Low frequency flutter may be tolerated up to about 100 hertz.
Jitter correcting apparatus has been known in connection with magnetic recording and reproducing systems. U.S. Pat. No. 3,639,689, issued to Doi, Feb. 1, 1972, discusses various approaches to this problem. In general, such apparatus controls a variable delay circuit inserted in the path of the reproduced signal by comparing the reproduced video signal or alternatively its phase to a corresponding reference signal, or by developing a jitter control signal from phase comparison operations. These circuit techniques differ markedly from that of the subject invention, which pertains to dejittering transmitted data typically in an encoded digital format.